1. Field
The present disclosure relates to a semiconductor buffer structure, a semiconductor device and method of manufacturing the semiconductor device using the semiconductor buffer structure.
2. Description of the Related Art
Conventional nitride-based semiconductor devices use a sapphire substrate. However, a sapphire substrate is relatively expensive. A sapphire substrate is also relatively difficult to manufacture into chips and has a relatively low electric conductivity. Furthermore, a sapphire substrate may not be easily manufactured into a relatively large size due to its tendency to warp at relatively high temperatures (e.g., during epitaxial growth) due to its relatively low thermal conductivity. In order to prevent the above problems, nitride-based semiconductor devices using a silicon (Si) substrate instead of a sapphire substrate have been developed. Since a Si substrate has a higher thermal conductivity than a sapphire substrate, the Si substrate is not as likely to warp at the higher temperatures used for growing a nitride thin film, thereby making it possible to grow a relatively large thin film on the Si substrate. However, when a nitride thin film is grown on a Si substrate, a dislocation density may be increased due to a mismatch in lattice constants between the Si substrate and the nitride thin film. Consequently, cracks may occur due to the tensile stress generated by the mismatch in thermal expansion coefficients between the Si substrate and the nitride thin film. Accordingly, many types of buffer structures have been studied in an attempt to grow nitride thin films, which have relatively high crystallinity and no cracks, on a Si substrate.